1. Field of the Invention
The present general inventive concept relates to an inspection apparatus for a thin film transistor (TFT) substrate, and more particularly, to an inspection apparatus capable of inspecting a defective pixel of a TFT substrate using deflection of an electron beam.
2. Description of the Related Art
A conventional inspection apparatus for inspecting a TFT substrate includes an oscilloscope probe controlled to contact the TFT substrate to analyze a waveform of a signal output by the probe when the probe is placed in contact with the TFT substrate. It takes relatively long time when inspecting the TFT substrate with the conventional inspection apparatus having the oscilloscope probe to be in contact with the TFT substrate during inspecting because the oscilloscope probe has to be moved mechanically. Further, the TFT substrate is likely to be damaged because the oscilloscope probe directly contacts the TFT substrate.
Accordingly, a contactless inspection apparatus without using the oscilloscope probe has been developed as an alternative to the conventional inspection apparatus using the oscilloscope probe in contact with the TFT substrate. The contactless inspection apparatus uses a voltage contrast of electron, that is, emits an electron beam to a TFT substrate and then detects a secondary electron reflected from the TFT substrate, thereby inspecting defects on the TFT substrate.
For example, inspection apparatuses detecting the secondary electron have been disclosed in Japanese Patent First Publication Nos. 2000-3142 and 1999-265678.
Such a contactless inspection apparatus can detect the secondary electron beam if a vacuum chamber accommodating the TFT substrate is maintained in a high vacuum state. That is, when a plurality of TFT substrates have to be inspected, the vacuum chamber should be highly vacuumized whenever each TFT substrate is placed inside the vacuum chamber for inspection. Hence, it takes a relatively long time to highly vacuumize the vacuum chamber.
Further, because equipment for highly vacuumizing the vacuum chamber is additionally provided, a size of the contactless inspection apparatus increases correspondingly.
Also, because the electron beam emitted from an electron gun is perpendicular to the surface of the TFT substrate, the position of the electron beam relative to the TFT substrate should be changed according to the size of the TFT substrate, since the TFT substrates may have different sizes.